This invention relates to surgical apparatus for applying force to the skin and is more particularly concerned with a method of load cycling a flap of skin to extend the length of said flap.
It has been found that, when a constant stretching force is applied to skin, the skin will stretch continuously. This creep of the skin is effected partly by extrusion of tissue fluid from between the collagen fibres as they align themselves in the direction of the stretching force, and parallel to each other. Up to 90% of the dry weight of the dermis is constituted by collagen fibres which have a highly convoluted arrangement when the skin is in a state of rest.
Initially, the rearrangement of collagen fibres is accomplished with ease, under low loads. As more of the collagen fibres become aligned, a greater stretching force is required to overcome the increased tension of the skin. Care, however, must be taken to avoid excessive stretching which can cause damage to the skin.
Additionally extensibility of the skin can be obtained by load cycling. With this method, tension is applied to the skin for several periods separated by intervals of relaxation. Each time that tension is applied, more collagen fibres are aligned in the direction of the stretching force and additional extension is produced. Typically, tension can be applied three or four times for three to four minutes each with the periods of tension application being separated by relaxation intervals of about a minute.
This technique can be used to close skin defects, such as produced by burn injury, in a relatively short time and with less discomfort than some previous techniques.